The invention relates to the use of a metal organosilicate polymer for the protection, from oxidation and/or electromagnetic radiation, of compounds sensitive to oxidation and/or to electromagnetic radiation.
It also relates to a fluorescent composition and to a marking composition comprising such a fluorescent composition and also to a composition for protecting from electromagnetic radiation.
Numerous compounds have properties which deteriorate by oxidation or by exposure to electromagnetic radiation, in particular during exposure to UV radiation.
This is thus the case with compounds of the family of the benzotriazoles and in particular 2-(2′-hydroxy-5′-methylphenyl)benzotriazole.
Indeed, this compound is an excellent protector from UV radiation because, under irradiation by UV radiation, the hydrogen bond conferring its aromaticity on it is broken and thus the compound absorbs UV photons. As, furthermore, the hydrogen bond is reformed over time, it is a compound absorbing UV photons which is regenerated.
However, this compound is very sensitive to oxidation and is decomposed and thus loses its properties of protecting from UV radiation.
Other compounds sensitive to oxidation and/or to electromagnetic radiation are fluorophoric compounds.
Fluorophoric compounds are used in particular for the marking of paper and textiles, either for combating counterfeiting or for the purposes of authentification or for simply identifying the date of manufacture of the paper or fabric, or also for identifying the manufacturer.
Paper, in particular for a notarial deed, and also textiles have a very long lifetime, of greater than fifteen years.
This is why the resistance to oxidation and to photoaging of the markers used is important.
Rare earths which are inorganic fluorophoric compounds have been used for this purpose of marking.
However, rare earths are easily identified by a simple analysis, which means that marking obtained with rare earths can be easily reproduced.
Organic fluorophoric compounds for their part are not easily identifiable by a simple analysis.
These organic fluorophoric compounds are also used for the biological labeling of biological reactions.
However, these compounds are sensitive to oxidation by oxygen, ozone and NOx, in particular.
They have thus been used in the presence of antioxidants, the aim of which is to scavenge the oxygen in all its forms.
However, the effectiveness of the antioxidant ceases when all the oxygen-scavenging molecules have been consumed by the oxygen molecules present.
Furthermore, and this is a disadvantage in particular for paper and textiles, organic fluorophoric compounds have another disadvantage: they are very sensitive to electromagnetic radiation, such as UV radiation, visible radiation and near infrared radiation.
Currently, in order to protect them, use is made of organic or inorganic additives which will screen out electromagnetic radiation but which will also limit the phenomenon of fluorescence.
However, finally, it is also known that the phenomena of oxidation or of photooxidation and aging by exposure to electromagnetic radiation are superimposed on one another and/or act synergistically to decompose the organic fluorophoric compounds, whether in solution or on various supports.
Furthermore, a family of compounds referred to indiscriminately as metal organosilicate, metal phyllosilicate clay, metal organosilicate polymer or polysilsesquioxane salt is known.
For example, U.S. Pat. No. 7,132,165 B2 describes the manufacture of compounds of this type from amine surfactants or from structuring agents. These compounds are described as being mesoporous compounds based on lamellar silica having a high thermal and hydrothermal stability.
These compounds are also described by L. Ukrainczyk et al. in “Template Synthesis and Characterization of Layered Al- and Mg-Silsesquioxanes”, J. Phys. Chem. B, 1997, 101, 531-539.
A method for the preparation of these compounds is described in this document: the silsesquioxane compounds were prepared by precipitation at ambient temperature by addition of an aqueous base to an alcoholic solution comprising a mixture of AlCl3 or of MgCl2 and of a trialkoxysilane with an n-dodecyl, n-octyl, n-pentyl, 3-methacryloyloxypropyl, isobutyl or phenyl functionality.
These compounds are described as being able to be used as absorbents, environmental barriers, polymer fillers, catalytic supports or chemical sensors.
Nicola T. Whilton et al., in “Hybrid lamellar nanocomposites based on organically functionalized magnesium phyllosilicate clays with interlayer reactivity”, J. Mater. Chem., 1998, 8(8), 1927-1932, also describe the preparation of such compounds by addition of organotrialkoxysilane to a solution of MgCl2.6H2O in ethanol and precipitation by a sodium hydroxide solution.
However, no application is described or suggested in this document for these compounds.
U.S. Pat. No. 5,342,876 also describes a process for producing such compounds, which are described as being spherical and porous silica granules which have an excellent ability to disperse in resins and thus make it possible to obtain films having an excellent transparency, which are resistant to flaking and which can be used as odor scavengers and as agent for controlling exudation.